There exist various techniques for manufacture of integrated circuits using laser radiation to fuse conductive links. Examples of such techniques appear in U.S. Pat. No. 4,387,503 to Aswell et al, U.S. Pat. No. 4,238,839 to Redfern et al, and U.S. Pat. No. 3,740,523 to Cohen et al.
There is described in applicant's pending Israel Patent Application No. 74108, filed Jan. 20, 1985, semiconductor devices including a collection of semiconductor elements and having fusible links interconnecting the collection of semiconductor elements, whereby selective fusing of the fusible links, as by a laser, defines the electronic function provided by the collection of semiconductor elements.
Laser etching of the type envisioned in the above mentioned examples must be highly specific and must enable etching of a conductor on a given layer without damaging the substrate or underlying conductors in different layers of the semiconductor device.
This requirement has been approached by optimization of dielectric layer thicknesses. Such optimization is described in Application Report 150 entitled "Optimization of Semiconductor Layer Thicknesses for Repair of RAMs" by Don Smart of Teradyne Inc. of Boston, Mass., U.S.A.
A detailed study of the optical interference in dielectric layers which separate metal films appears in "Laser vaporization of metal films-Effect of optical interference in underlying dielectric layers" by J. C. North, Journal of Applied Physics, Vol. 48, No. 6, June 1977, pages 2419-2423.
Silicon nitride has been used in connection with microelectronic fabrication for insulation and surface protection. It has not heretofore been identified for use in optical coating.